Rename book/chapter/verse fields in pages JSON to be consistent

[SLaks]

The Ref type uses b, c, and v.

In contrast, the JSON files in data/pages use book, chapter, and verse.

This makes these objects hard to use together. As a followup to my Calendar refactor (#129; this will replace all references to these fields), can you please rename the fields in the JSON generator to be consistent?

Please also delete the aliyot field from the pages; this is already unused.

These will also reduce the filesize.